Furnace



Oct. 28 1924. 1,513,065

J. 5. PEARCE FURNACE Filed July 19. 1923 INVENTOR Jab/7 5.1%0/66.

BY r "3 ATTORNEY Patented Got. 28, 1924.

U NETED STATES JOHN S. PEARCE, OF- VANCOUVER, BRITISH COLUMBIA, GA'NADAV FURNACE.

Application filed July 19,

T0 at whom it may concern:

Be it known that I, JOHN S. PEARCE, citizen of the Dominion of Canada, residing at Vancouver, in the Province of British Columbia, Canada, have invented certain new and useful Improvements in Furnaces, of which the following is aspecification.

This invention relates to a furnace for the efficient combustion of wood refuse or other fuel, such as low grade coal, lignite, peat or the like, Which, for satisfactory consumption, require the delivery of air for combustion at variouspartsof the furnace or the combustion chamber. In order to effectively consume the gases as given off during the changing conditions of the fire level, and at the same time to deliver the products of combustion at a high temperature to the boiler or other purpose to which they are to be applied, the airdelivery is dependent on the amount of fuel on the. e a-t The feature of improvement in this invention to which attention is particularly directed lies in the means whereby the varying height and consequent condition of the fuel in the furnace chamber automatically regulates the flow of the furnace gases to suit the requirements of combustion under these changing conditions.

This result is attained by the use of a furnace chamber which is relatively deep and narrow and to this chamber air for combustion is delivered primarily through stepped grate bars, and secondarily through apertures in both side walls ofthe furnace chamber, which secondary supply of air is heated before delivery by its passage through the ducts in the walls of the furnace chamber. The hot gases from the furnace chamber are delivered from the back of the chamber through two exits, one ap-' proximately level with; the gratebars and; the other from the upper part. of the chamb'er' immediately" over: the first named. exit, the upper exit delivering into the loweror direct: exit approximate a third delivery of air to complete the combustion of the gases from the furnace.-

The. ports through which the secondary supply" of air is. delivered" areso located that as the condition of the fire on the grate approaches its lower limit, they are partially uncovered, whereby the combustion of the incandescent fuel, being directly supplied with a r, is n ensifi d endflthe flame of t is 1923; Serial No. 652,589.

rapid combustion passes throughthe upper exit and heats to'a high temperature a mass of loosely stacked refractory material in the passage before it is delivered to the main or lower exit. 7

When the furnace is re-charged the vola-' tile'gases and vapoursfromthe green fuel, as they pass through the highly heated upper exit, receive suflicient heat tobe entirely consumed as they are delivered into the main exit;

The means by. which these several results are attained is fully described in the following specification, reference being made to the drawings by which it is accompanied, in which: I

Fig. 1 isa sectional plan showing theaapplication of the furnace to the stack of a lime-kiln, being a section on the line 11 in Fig. 2.

Fig. Qis a vertical section on the line 22 in Fig. 1, and

Fig. 3 is'a vertical cross section on the .line 3-8 in Fig. 1.

. In these drawings 2 represents a deep and relatively narrow furnace-chamber havingstepped grate bars 3, a closable doorway 4: through which the fuel ischarged and a closable door 5 affording access to below the grate.

From the back of this chamber 2 at the approximate level of the. grate bars 3' a relatively large passage 6 into the stack 7 of the lime-kiln, and from the upper part of the chamber 2 a smaller duct 8'delivers into a space 9 and therefrom through a duct 10 into the upper part of the directpassage 6. The space 9 isfilled with'loosely packed, refractory material, such as spaced apart fire-brick through which the gases are constrained to pass on their way to the direct. passage 6.

A draw tunnel. 11,. closable; at its upper end, affords. access to'the flue 6 for. samplmg the lime: and? for: clearing away undue accumulation. of lime; i -5on1; the: fine.

All? for. combustion is: admitted through. a pipe; or. duct12. under control. of. a damper 13, and is delivered at 14; into the space be; low the grate, and: through branch. ductsle in; each side wall ofithefurnaceto. apertures located. about: level with; the upper side of the direct; passage. 6,. that is,slightly above the lower fuel line 16;. (seezFig; 2). A. duct 17., formed. in the; wall; or floor ofthefurdelivers directly nacechamber, extends: along below the draw tunnel 11 through which duct air is deliv- V ered from the space below the grate into the outer end of the draw tunnel 11 and through it into the direct passage 6 from the furnace to the kiln. In this duct 17 interspaced brick may be placed to more effectively heat the air passing through it.

vVherethe furnace is applied to a limekiln, as shown in the drawing, air is also delivered through an aperture 18 into the kiln 7 immediately below the direct passage 6 from the furnace, which has the two-fold effect of cooling the burnt lime and supplying a supply of heated air to aidcombustic-n of gases in the kiln.

This threefold delivery of the air for combustion to below the grate at 14 into the combustion zone of the furnace through its side walls at 15, and through 17 and 11 into the direct passage 6 from the furnace to the kiln, is productive of a favourable cycle of combustion which may be described as follows:

Assume the furnace to have been kindled for a sufficient time to be in full working order, and that the fuel in the furnace chamber 2 has settled down, in a state of incandescence, to approximately the upper edge of the direct passage 6 to the kiln. Under these conditions the secondary supply of air admitted through the ducts 15 in both side 'walls of the furnace chamber considerably increases the combustion of the fuel in the space above it, the flame from which active combustion passes through the duct 8 from the upper part of this chamber and through the interspaced refractory material 9 and is delivered through the duct 10into the direct passage 6, to pass to the kiln with the gases drawn directly therethrough from the furnace and consumed with the hot air delivered into that passage through the draw tunnel 11.

The heat of this active combustion is imparted to the refractory material 9 through the interspaces of which it has to pass.

Thereafter as the incandescent fuel sinks to the lower line 16, the furnace is recharged to the level of the full line 19. When the fuel is filled to this line 19 en trance to direct passage 6 from the space above the fuel line is obstructed, and the volatile gases and vapours driven ofi from the green fuel must pass from the upper part of the furnace chamber 2 through the duct 8 and through the interspaces of the refractory material 9, which has been highly heated by the previous passage of the flame through it. These highly heated unconsumed gases mixing with the third supply of fresh heated air delivered through the draw tunnel 11 are effectively consumed before delivery to the kiln.

' As the fuel 6 in the furnace chamber sinks, the cycle above described is repeated.

The walls of the ducts 8, 9 and 10 are thus alternately highly heated by the flaming isfactory combustion under the changing conditions of the fire, and particularly for the combustion of low grade fuels which are otherwise largely waste products, or which are difficult to find a market for.

The furnace chamber is made narrow and deep to enable the heated air for combustion to be delivered effectively to the combustion zone of the fuel. 7

In applying this'furnace to a stack limekiln, it is preferably applied in pairs, one pair to each side of the kiln, and the space above the fuel line of each pair is connected together. That is, the partition wall between each pair is common to both, and the other pair of furnaces delivers into the opposite side of the kiln 7.

It will be noticed that the hot gases from the furnaces are delivered at- 6 into the stack 7 of the kiln at some little distance from the lower end through which the burnt lime is withdrawn, so that as the lime is burnt it settles down below the passages through which the hot gases are delivered and has an opportunity to slowly cool before it is withdrawn through the drop door in the bottom of the stack.

It will be further noticed that the air delivered at 18 to the kiln is relatively cool, so that the delivery of this supply of cool air, not only cools the burnt lime, but is heated by contact therewith before it passes upward through the lime being burnt, where it is consumed and the heat of its combustion furthers the burning of the lime.

Although illustrated and described as applied to a lime-kiln, I do not desire to be confined to such use of the furnace, as the essential features of construction are applicable to any purpose where the nature of the fuel to be used will render it advantageons, for example, brick or pottery kilns, an nealing ovens or steam generators, and al though it may be used as a single furnace, it is preferable, owing to its relatively narrow width, to apply it in pairs.

Having now particularly described. my invention, I hereby declare that what I claim as new and desire to be protected in by Letters Patent,- is:

1; A furnace for the combustion of solid fuel and the delivery of the hot gases therefrom, comprising a relatively deep and narrow chamber having walls of heat non-conducting material, a grate in the lower part of such chamber, a closable opening through which the fuel may be delivered on the grate, a direct exit for the fuel gases adjacent the level of the grate, a second exit for the fuel gases delivering into the direct exit, means for delivering air for combustion to below the grate, means for heating and delivering air through the side walls of the furnace adj acent the direct exit, and means for heating and delivering air into the direct exit adjacent the connection of the second exit thereto.

2. A furnace for the combustion of solid fuel and the delivery of the hot gases therefrom, comprising a relatively deep and narrow chamber having Walls of heat non-conducting material, a grate stepped downward from the front toward the back, a closable opening through which fuel may be delivered on the grate, a direct exit for the fuel gases adjacent the level of the grate, a second exit for the fuel gases from the upper part of the chamber and delivering into the direct exit, means for delivering air for combustion to below the grate, means for heating and delivering air through the side walls of the furnace adjacent the direct exit, and means for heating and delivering air into the direct exit adjacent the connection of the second exit thereto.

In testimony whereof I affix my signature.

JOHN S. PEARCE. 

